1. Technical Field
The present disclosure relates to an electrosurgical return pad, and more particularly, the present disclosure relates to an electrosurgical return pad with contact quality monitoring for use during electrosurgery.
2. Background of Related Art
Electrosurgery is the application of electricity and/or electromagnetic waves to cut or modify biological tissue during a surgical procedure. Generally, electrosurgery utilizes an electrosurgical generator, a return electrode, and a source electrode. The electrosurgical generator produces an electromagnetic wave, typically above 100 kilohertz, between the return and source electrodes when applied to tissue. The electromagnetic wave created therebetween dissipates energy as heat as it travels from one electrode to the other. Electromagnetic frequencies above 100 kilohertz are employed to avoid muscle and/or nerve stimulation.
During electrosurgery, current generated by the electrosurgical generator is conducted through patient tissue between the two electrodes. The current causes the tissue to heat up as the electromagnetic waves overcome the tissue impedance. Although, many other variables affect the total heating of the tissue, usually with more current density, increased heating results. Current can be used for cutting, dissection, ablation, arresting blood loss and coagulation, and are well-known.
The two basic types of electrosurgery employed are monopolar and bipolar electrosurgery. Both types use an “active” and a “return” electrode, although the distinction is not always necessary. In bipolar electrosurgery, the surgical instrument has an active electrode and a return electrode on the same instrument or in very close proximity, usually causing current to flow through a smaller amount of tissue. In monopolar electrosurgery, the return electrode is located elsewhere on the patient's body and is usually not part of the surgical instrument itself. In monopolar electrosurgery, the return electrode is part of a device referred herein as a return pad.
The return pad is intended to lower the current density in nearby tissue when current flows between the return pad and the patient's tissue. The current density through the tissue near the return pad is related to the impedance between the tissue and the return pad. This impedance is referred to herein as contact impedance. When the surface area of the return electrode contacting the skin is reduced, increases in current density may heat tissue up to the point of possibly causing skin damage. Maintaining low contact impedance helps prevent electrosurgery related injuries.
Generally, resistive electrodes tend to have more uneven heating than capacitive electrodes. Because electricity tends to conduct through the path of least resistance, more current tends to conduct through the tissue near the edge of a resistive electrode that is closest to the active electrode, creating more localized heat. This is known as the “edge effect”. Although, capacitive electrodes tend to have more uniform heating than resistive electrodes, measuring contact quality has been more difficult.